Secure processor design goes back to the IBM 4758, which embedded certain protected information, or “secrets,” in a read only memory (ROM), protected the processor with an enveloping anti-tamper mesh, which destroyed the secrets upon tamper detection. Additionally, the IBM 485 employed a one-way ratcheting process to use the secrets in booting operating systems and loading application software.
Fabrication of such devices, generally requires that the protected information be installed prior to application of the anti-tamper mesh, for example, during fabrication. At least one disadvantage with such an approach is that the fabrication facility must be protected from unauthorized to ensure that the secrets are not discovered, or otherwise tampered with. Additionally, modification of such protected information can be limited by the presence of any anti-tamper mesh.